The invention relates to a process for producing and a method for using a corrosion inhibitor composition for reducing the corrosion rate of a metal by a fluid having at least one corrosion agent. More specifically, the invention relates to synthesis and use of one or more quaternized compounds having an imino or amido moiety, for example quaternized imidazoline(s) having an imino or amido moiety, in such a corrosion inhibitor composition used in oil and gas-field applications.
In order to reduce the rate of corrosion of metals, and particularly metals containing iron, from one or more metal corrosion agents present in a fluid (i.e., a gas, liquid, slurry or a mixture thereof a corrosion inhibitor is frequently introduced into the fluid to reduce the rate of corrosion of the metal vessel, pipeline and/or equipment used to store and transport the fluid. In oil and gas-field applications, for example, corrosion inhibitors are added to a wide array of systems, including without limitation, cooling systems, refinery units, pipelines, steam generators and oil or gas producing units in efforts to combat a variety of types of corrosion.
One example of corrosion, among others, typically encountered in the transport of a fluid containing one or more corrosion agents (hereinafter simply referred to as xe2x80x9cfluidxe2x80x9d) is flow-induced corrosion. In the case of flow-induced corrosion, the degree of corrosion that occurs is presently believed to depend on a variety of factors, including the corrosiveness of the fluid itself, the metallurgy of the pipeline and the shear rate, temperature, and pressure of the fluid.
Also, to the extent that a corrosion inhibitor is used, the inhibitor""s ability to reduce the rate of corrosion of a metal from flow-induced corrosion, among other types of corrosion, is presently believed to depend on at least two factors. One factor is the inhibitor""s chemical affinity for the metal surface. A second factor is the inhibitor""s resistance to breakdown under high shear conditions. Therefore it is currently believed that the rate of corrosion, especially flow-induced corrosion, of a metal more likely will be reduced where the inhibitor has good chemical affinity for the metal surface and can resist breakdown under high shear conditions. Many inhibitors have been developed to reduce corrosion. However, their activity is sufficiently low that higher concentrations are oftentimes required to effectively treat a pipeline, most particularly where flow-induced corrosion is a problem, thereby increasing operating costs.
Conventionally, the presence of a free amine moiety in inhibitors, such as that described in U.S. Pat. No. 5,322,640, has been thought to be desirable because a pendant alkyl amine group would have at least one free amine (e.g., a NH2 group) available for interaction with a metal surface. Accordingly, until the disclosure of the present invention, those skilled in the art of synthesizing corrosion inhibitors refrained from further reacting the intermediate product produced in U.S. Pat. No. 5,322,640 and/or producing imidazoline derivatives where the group pendant to the imidazoline ring contains either an imino moiety, generally described as xe2x80x94Nxe2x95x90CHxe2x80x94R or, an amido moiety, generally described as xe2x80x94Nxe2x80x94(Cxe2x95x90O)xe2x80x94R.
Conventionally, such imino and amido imidazolines and their derivatives generally were considered to have little to no corrosion inhibition activity or potentially to have detrimental effects on the reaction product""s corrosion inhibition activity. Specifically, it was understood by those skilled in the art that the lack of a pendant group with a heteroatom (e.g., nitrogen, sulfur or oxygen) having a pair of nonbonding electrons freely available for interaction with a metal surface would have an adverse affect on the performance of the inhibitor. In such instances, the pendant group would lose its freely available pair of nonbonding electrons on the heteroatom of the pendant group because of electron delocalization. In turn, it was thought such electron delocalization would reduce the compound""s ability to interact with a metal surface, and thereby reduce its overall inhibition activity.
A corrosion inhibitor is desired that has improved inhibition performance as compared with inhibitors presently used for treating systems experiencing flow-induced corrosion, among other corrosion problems.
A substantial number of corrosion inhibitors have been disclosed for reducing the rate of corrosion of metal-containing storage and transport systems. More specifically, a number of corrosion inhibitors have been disclosed, most particularly for treating flow-induced corrosion, including, among others, quaternized imidazolines. A need exists, however, for a corrosion inhibitor with improved reduction in the rate of corrosion, for example flow-induced corrosion, of metals.
According to one aspect of the present invention, there is provided a process for producing a composition comprising at least a quaternized compound, comprising the steps of: (a) selecting a first organic compound from the group consisting of: (i) substituted and unsubstituted, saturated and unsaturated fatty acids having from about 6 to about 30 carbon atoms; (ii) substituted and unsubstituted, saturated and unsaturated fatty acids having from about 6 to about 30 carbon atoms, wherein said fatty acid is at least oxygenized, sulfurized or phosphorylized; and (iii) combinations thereof; (b) selecting an alkyl polyamine from the group having the general formula:
H2Nxe2x80x94CH2xe2x80x94(CH2)pxe2x80x94NHxe2x80x94(CH2)qxe2x80x94NH2 
wherein p=1 to about 5 and q=2 to about 10; (c) selecting a second organic compound from the group consisting of (i) carbonyl compounds having from 2 to about 31 carbon atoms; (ii) fatty acids having from 2 to about 30 carbon atoms; and (iii) combinations thereof; (d) selecting a third organic compound from the group consisting of (i) substituted and unsubstituted, xcex1,xcex2-unsaturated carboxylic fatty acids, and amide and ester derivatives thereof, having from about 3 to about 11 carbon atoms; (ii) substituted and unsubstituted, xcex1,xcex2-unsaturated sulfonic and phosphonic fatty acids having from about 2 to about 11 carbon atoms; and (iii) combinations thereof; (e) mixing said first organic compound and said alkyl polyamine in a mole ratio in a range of from about 0.6:1 to about 1.2:1 to produce at least one intermediate compound, wherein said mole ratio is the total moles of said first organic compound to the total moles of said alkyl polyamine; (f) mixing said at least one first intermediate compound with said second organic compound to produce a second intermediate compound; and (g) mixing said second intermediate compound with said third organic compound to produce said composition.
According to another aspect of the present invention, there is provided a composition produced by the process described above.
According to a further aspect of the present invention, there is provided a method of using the composition produced by the process described above for reducing the corrosion rate of a metal by a fluid having at least one corrosion agent, said method comprising: (a) introducing said composition into said fluid; and (b) contacting said metal with the fluid of step (a).
According to yet another aspect of the present invention, there is provided a method of using a corrosion inhibitor composition for reducing the corrosion rate of a metal by a fluid having at least one corrosion agent, said method comprising: (a) introducing said corrosion inhibitor composition into said fluid, said inhibitor composition having at least one compound wherein said compound is a quaternized compound having the general formula: 
wherein, R1 is a moiety selected from the group consisting of: (i) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms; (ii) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms, wherein said alkyl group is at least oxygenized, sulfurized or phosphorylized; and (iii) combinations thereof; R2 is an imino moiety; R3 is a moiety selected from the group consisting of xe2x80x94CO2H, xe2x80x94SO3H, xe2x80x94PO3H2, xe2x80x94CO2R7, xe2x80x94CONH2, xe2x80x94CONHR7 and xe2x80x94CON(R7)2 groups and combinations thereof; each R7 is independently selected from the group consisting of hydrogen and linear and branched alkyl aryl, alkylaryl, cycloalkyl and heteroaromatic groups having from 1 to about 10 carbon atoms, and combinations thereof; R8 is hydrogen or a linear alkyl group having from 1 to about 10 carbon atoms; and n=0 to about 8, p=1 to about 5 and q=2 to about 10; and (b) contacting said metal with the fluid of step (a).
Accordingly, one aspect of the invention, discussed below, relates to methods for synthesizing quaternized imidazolines as well as other related quaternized compounds described by the following general formula, hereinafter referred to as compound A: 
where R1 is a moiety selected from the group consisting of (i) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms; (ii) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms, wherein said alkyl group is at least oxygenized, sulfurized or phosphorylized; and (iii) combinations thereof; R2 is a moiety selected from the group consisting of imino and amido groups; R3 is a moiety selected from the group consisting of xe2x80x94CO2H, xe2x80x94SO3H, xe2x80x94PO3H2, xe2x80x94CO2R7, xe2x80x94CONH2, xe2x80x94CONHR7 and xe2x80x94CON(R 7)2 groups and combinations thereof; each R7 is independently selected from the group consisting of hydrogen and linear and branched alkyl, aryl, alkylaryl, cycloalkyl and heteroaromatic groups having from 1 to about 10 carbon atoms, and combinations thereof; R8 is hydrogen or a linear alkyl group having from 1 to about 10 carbon atoms; and n=0 to about 8, p=1 to about 5 and q=2 to about 10. It is to be understood that the range of carbon atoms specified for each group described herein refers to the main chain of the alkyl groups, and does not include carbon atoms that may be contributed by substituents.
Many quaternary ammonium compounds are acyclic, having the general formula R4N+Xxe2x88x92, and are a type of ionic organic compound with at least one nitrogen atom. However, heterocyclic compounds with at least one nitrogen atom also can be quaternary ammonium compounds.
In the case of acyclic quaternary ammonium compounds, a nitrogen is covalently bonded to four organic groups and bears a localized positive charge that is balanced by a negative counterion. The negative counterion may be either attached to or unattached to, but still associated with, the rest of the compound.
In the case of heterocyclic ammonium compounds, at least one nitrogen has four bonds, which are either (a) each single bonds or (b) two single bonds and a double bond. The present invention produces heterocyclic quaternized ammonium compounds, which, for convenience, are depicted as having two single bonds and a double bond with the double bond shown as a resonance type structure, indicating that it is delocalized between two nitrogen atoms of the same heterocyclic ring. However, it will be understood by those skilled in the art that the specified groups pendant to each nitrogen, could also, in whole or in part, be pendant to a single nitrogen.
The quaternized compounds A may be used alone or in combination with other corrosion inhibitors and/or corrosion inhibitor formulation substances, including, without limitation, solvents, surfactants, and quaternized salts, which are more fully described below.
All derivatives of compound A have heterocyclic rings containing two nitrogen atoms. The heterocyclic ring of compound A preferably has from about 3 to 7 carbon atoms, more preferably from about 3 to 5 carbon atoms and most preferably 3 carbon atoms. Compound A is a quaternized imidazoline when there are 3 carbon atoms, a quaternized tetrahydropyrimidine when there are 4 carbon atoms, and so on.
As specified above, the derivative of compound A may have one group pendant to the first nitrogen atom of the heterocyclic ring containing a xe2x80x94CO2H, xe2x80x94SO3H, xe2x80x94PO3H2, xe2x80x94CO2R7, xe2x80x94CONH2, xe2x80x94CONHR7 and xe2x80x94CON(R7)2 group and a second group pendant to the second nitrogen atom of the heterocyclic ring containing an imino or amido group.
Also, the derivative of compound A may have a group pendant to the apex carbon bridging the first and second nitrogen of the heterocyclic ring that is (i) a substituted or unsubstituted, saturated or unsaturated alkyl group having from about 5 to about 29 carbon atoms; (ii) a substituted or unsubstituted, saturated or unsaturated, oxygenized, sulfurized or phosphorylized alkyl group having from about 5 to about 29 carbon atoms; or (iii) a combination thereof. Generally, preferred R1 moieties include (a) unsubstituted, unsaturated alkyl groups having from about 7 to about 23 carbon atoms, (b) substituted, unsaturated alkyl groups having from about 7 to about 23 carbon atoms, and (c) sulfurized unsubstituted, saturated or unsaturated alkyl groups having from about 7 to about 23 carbon atoms. More preferred R1 moieties include (a) unsubstituted, unsaturated alkyl groups having from about 11 to about 23 carbon atoms, and (b) substituted, unsaturated alkyl groups having from about 11 to about 23 carbon atoms. Most preferred R1 moieties include unsubstituted, unsaturated alkyl groups having from about 17 to about 21 carbon atoms.
Examples of suitable substituents include, without limitation, OH, SH, halogen atoms, alkyl, aryl, alkylaryl and heteroaromatic groups and, combinations thereof.
The group pendant to the first nitrogen atom of the heterocyclic ring has at least 2 carbon atoms, one of which may be substituted with a linear alkyl group having from 1 to about 10 carbon atoms. The pendant group may or may not have a conjugated portion with up to 8 carbon atoms which may or may not be substituted with a linear or branched alkyl, aryl, alkylaryl, cycloalkyl or heteroaromatic group having from 1 to about 10 carbon atoms or a combination thereof.
The group pendant to the first nitrogen atom of the heterocyclic ring also contains a xe2x80x94CO2H, xe2x80x94SO3H, xe2x80x94PO3H2, xe2x80x94CO2R7, xe2x80x94CONH2, xe2x80x94CONHR7 or xe2x80x94CON(R7)2 moiety. Preferably, the group pendant to the first nitrogen atom of the heterocyclic ring contains a carboxylate, sulfonate or phosphonate moiety, more preferably contains a carboxylate or sulfonate moiety and most preferably contains a carboxylate moiety.
Preferably, the group pendant to the second nitrogen atom of the heterocyclic ring contains a linear or branched alkyl group having from about 2 to about 10 carbon atoms, more preferably contains a linear or branched alkyl group having from about 2 to about 6 carbon atoms and most preferably contains a linear alkyl group having from about 2 to about 4 carbon atoms.
Preferably, the group pendant to the second nitrogen atom of the heterocyclic ring also contains an imino or amido moiety, and more preferably contains an imino moiety.
Therefore, more particularly, one embodiment of a compound A derivative contains an imino R2 moiety, in the group pendant to the second nitrogen atom of the heterocyclic group, having the following general formula: 
where R5 is selected from the group consisting of linear alkyl, branched alkyl, cycloalkyl, aromatic, alkylaryl, heteroaromatic and heterocyclic groups having from 1 to about 30 carbon atoms, and combinations thereof. Preferably, R5 is an alkyl group having from 1 to about 30 carbon atoms, more preferably is a linear or branched alkyl having from 1 to about 11 carbon atoms and most preferably is a linear or branched alkyl group having from 1 to about 5 carbon atoms.
Another embodiment of a compound A derivative contains an amido R2 moiety, in the group pendant to the second nitrogen atom of the heterocyclic group, having the following general formula: 
where R4 is a moiety selected from the group consisting of (i) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms; (ii) substituted and unsubstituted, saturated and unsaturated alkyl groups having from about 5 to about 29 carbon atoms, wherein said alkyl group is at least oxygenized, sulfurized or phosphorylized; and (iii) combinations thereof. It is to be understood that the range of carbon atoms specified for each group described herein refers to the main chain of the alkyl groups, and does not include carbon atoms that may be contributed by substituents.
Generally, preferred R4 moieties include (a) unsubstituted, unsaturated alkyl groups having from about 7 to about 23 carbon atoms, (b) substituted, unsaturated alkyl groups having from about 7 to about 23 carbon atoms, and (c) sulfurized unsubstituted, saturated or unsaturated alkyl groups having from about 7 to about 23 carbon atoms. More preferred R4 moieties include (a) unsubstituted, unsaturated alkyl groups having from about 11 to about 23 carbon atoms, and (b) substituted, unsaturated alkyl groups having from about 11 to about 23 carbon atoms. Most preferred R4 moieties include unsubstituted, unsaturated alkyl groups having from about 17 to about 21 carbon atoms.
For example, one of the most preferred derivatives of compound A is a quaternized imino imidazoline having the following formula, hereinafter referred to as compound A1: 
where R1 is C17H33, R2 is NCHCH2CH3, R3 is COOxe2x88x92, R8 is hydrogen and n=0, p=1 and q=2 in formula A.
Another example of a preferred derivative of compound A is a quaternized amido imidazoline having the following formula, hereinafter referred to as compound A2: 
where R1 is C17H33, R2 is NHCOC17H33, R3 is COOxe2x88x92, R8 is hydrogen and n=0, p=1 and q=2 in formula A.
The synthesis of compound A derivatives, and more specifically, of the illustrative compounds, A1 and A2, described above is discussed more fully below. However, it should be understood that commercial manufacture of compound A will typically lead to a mixture of final products resulting from an incomplete cyclization step and competing reaction pathways that can yield compound A. Accordingly, a mixture of compounds includes at least a compound A derivative in combination with other compounds, including, without limitation, some unreacted starting material, some intermediate mono-, di- and/or polyamides arising from the reaction pathway for compound A derivatives and possibly other derivatives produced by competing reaction pathways.
The quaternized compounds having a moiety selected from the group consisting of imino and amido groups can be made using a wide array of organic compounds. Suitable organic compounds for practicing the invention are discussed below.
The first type of organic compound is generally selected from the class of fatty acids. More specifically, the fatty acids useful for practicing the invention can be selected from the group consisting of substituted and unsubstituted, saturated and unsaturated fatty acids having from about 6 to about 30 carbon atoms; substituted and unsubstituted, saturated and unsaturated fatty acids having from about 6 to about 30 carbon atoms, wherein the fatty acid is at least oxygenized, sulfurized or phosphorylized; and combinations thereof. It is to be understood that the range of carbon atoms specified for each group described herein refers to the main chain of the acid, and does not include carbon atoms that may be contributed by substituents.
Generally, preferred fatty acids of the first type include (a) unsubstituted, unsaturated fatty acids having from about 8 to about 24 carbon atoms, (b) substituted, unsaturated fatty acids having from about 8 to about 24 carbon atoms and (c) sulfurized unsubstituted, saturated or unsaturated fatty acids having from about 8 to about 24 carbon atoms. More preferred fatty acids of the first type include (a) unsubstituted, unsaturated fatty acids having from about 12 to about 24 carbon atoms and (b) substituted, unsaturated fatty acids having from about 12 to about 24 carbon atoms. Most preferred fatty acids of the first type include unsubstituted, unsaturated fatty acids having from about 18 to about 22 carbon atoms.
The alkyl polyamine(s) that can be used to practice the invention can be selected from the group having the following general formula:
H2Nxe2x80x94CH2xe2x80x94(CH2)pxe2x80x94NHxe2x80x94(CH2)qxe2x80x94NH2 
wherein p=1 to about 5 and q=2 to about 10.
Generally, preferred alkyl polyamines include those where p=1 to 2 and q =2 to 3. More preferred alkyl polyamines include p=1 and q=2 to 3. Most preferred alkyl polyamines include those where p=1 and q=2.
To produce a composition comprising an amine intermediate for a quaternized compound having an imino or amido moiety, the mole ratio of the first organic compound to the alkyl polyamine may be selected from the range of from about 0.6:1 to about 1.2:1, hereinafter referred to as the IA mole ratio range. As used herein, IA mole ratio means the ratio of the total number of moles of the first organic compound to the total number of moles of alkyl polyamine used in a process for making an amine intermediate for a quaternized compound having an imino or amido moiety. Generally, the preferred IA mole ratio range of the first organic compound to the alkyl polyamine is selected from the range of from about 0.65:1 to about 1:1. The more preferred IA mole ratio range of the first organic compound to the alkyl polyamine is selected from the range of from about 0.7:1 to about 0.9:1. The most preferred IA mole ratio range of the first organic compound to the alkyl polyamine is selected from the range of from about 0.75:1 to about 0.8:1.
It should be understood that the terms xe2x80x9cmixxe2x80x9d, xe2x80x9cmixedxe2x80x9d or xe2x80x9cmixingxe2x80x9d as used herein are intended to embrace all synthesis procedures, including, without limitation, batch, continuous, in-situ, interfacial and/or solution type processes and combinations thereof. Moreover, such terms and reference to any intermediates produced are used for convenience and for clarifying the scope of the Applicant""s invention. Accordingly, such terms should not be construed to limit the claimed invention to: (a) any particular sequence of reaction steps suggested herein, or (b) the production and/or separation of any specified amount of intermediate(s) for any specified length of time as a prerequisite to a subsequent process step.
The first intermediate produced by mixing the first organic compound with the alkyl polyamine is then mixed with a second organic compound to produce either an imino intermediate or an amido intermediate.
To produce a quaternized compound having an imino moiety, the amine imidazoline intermediate mixture produced from the first organic compound and the alkyl polyamine is mixed with a second organic compound. In the case of a quaternized imino compound, the second organic compound is a carbonyl compound selected from the group consisting of aldehydes and ketones having from 2 to about 31 carbon atoms. Preferably, the carbonyl compound is selected from the group consisting of linear alkyl, branched alkyl, cycloalkyl, aromatic, heteroaromatic and heterocyclic aldehydes and ketones, and combinations thereof. More preferably, the carbonyl compound is selected from the group consisting of linear alkyl, branched alkyl, cycloalkyl, aromatic, heteroaromatic and heterocyclic aldehydes.
To produce a quaternized compound having an amido moiety, the amine imidazoline intermediate mixture produced from the first organic compound and the alkyl polyamine is mixed with a second organic compound. In the case of a quaternized amido compound, the second organic compound can be selected from the group consisting of (i) substituted and unsubstituted, saturated and unsaturated fatty acids having from about 2 to about 30 carbon atoms; (ii) substituted and unsubstituted, saturated and unsaturated fatty acids having from about 2 to about 30 carbon atoms, wherein the fatty acid is at least oxygenized, sulfurized or phosphorylized; and (iii) combinations thereof. It is to be understood that the range of carbon atoms specified for each group described herein refers to the main chain of the acid, and does not include carbon atoms that may be contributed by substituents.
Generally, preferred second organic compounds for synthesis of the quaternized amido compounds include (a) unsubstituted, unsaturated fatty acids having from about 2 to about 20 carbon atoms, (b) substituted, unsaturated fatty acids having from about 2 to about 20 carbon atoms and (c) sulfurized unsubstituted, saturated or unsaturated fatty acids having from about 2 to about 20 carbon atoms. More preferred organic compounds include (a) unsubstituted, unsaturated fatty acids having from about 2 to about 10 carbon atoms and (b) substituted, unsaturated fatty acids having from about 2 to about 10 carbon atoms. Most preferred organic compounds include unsubstituted, unsaturated fatty acids having from about 2 to about 10 carbon atoms.
Examples of suitable substituents include, without limitation, OH, SH, halogen atoms, alkyl, aryl, alkylaryl and heteroaromatic groups, and combinations thereof.
The resultant imino or amide intermediate produced by mixing the first intermediate with the second organic compound is then mixed with a third organic compound to produce a quaternized compound having an imino or amido moiety, respectively.
The third type of organic compound is generally selected from the class of xcex1,xcex2-unsaturated fatty carboxylic acids and amide and ester derivatives thereof, xcex1,xcex2-unsaturated fatty sulfonic or phosphonic acids, and combinations thereof. More specifically, the third type of organic material useful for practicing the invention can be selected from the group consisting of (i) substituted and unsubstituted, xcex1,xcex2-unsaturated carboxylic fatty acids, and amide and ester derivatives thereof, having from about 3 to about 11 carbon atoms; (ii) substituted or unsubstituted, xcex1,xcex2-unsaturated sulfonic and phosphonic fatty acids having from about 2 to about 11 carbon atoms; and (iii) combinations thereof. It is to be understood that the range of carbon atoms specified for each group described herein refers to the main chain of the acid or acid derivative, and does not include carbon atoms that may be contributed by substituents.
Generally, preferred xcex1,xcex2-unsaturated carboxylic fatty acids and amide and ester derivatives thereof, and xcex1,xcex2-unsaturated sulfonic and phosphonic fatty acids are (a) unsubstituted and have from about 2 to about 9 carbon atoms, and (b) substituted and have from about 2 to about 9 carbon atoms. More preferred xcex1,xcex2-unsaturated carboxylic fatty acids and amide and ester derivatives thereof, and xcex1,xcex2-unsaturated sulfonic and phosphonic fatty acids are (a) unsubstituted and have from about 2 to about 7 carbon atoms, and (b) substituted and have from about 2 to about 7 carbon atoms. Most preferred xcex1,xcex2-unsaturated carboxylic fatty acids and amide and ester derivatives thereof, and xcex1,xcex2-unsaturated sulfonic and phosphonic fatty acids are unsubstituted and have from about 2 to about 5 carbon atoms.
Examples of suitable substituents include, without limitation, alkyl, aryl, alkylaryl, cycloalkyl and heteroaromatic groups, and combinations thereof.
Generally, preferred types of acid groups for selecting xcex1,xcex2-unsaturated fatty acids are carboxylic and sulfonic acids, while the most preferred acid group is carboxylic acid.
To produce a quaternized compound having a moiety containing a hydrocarbon and carbonyl, sulfonyl or phosphonyl group, the imino or amide intermediate mixture is mixed with one or more of the xcex1,xcex2-unsaturated fatty acids or acid derivatives, described above as the third organic compound. Preferably, the relative amounts of the imino or amide imidazoline mixture and the third organic acid or acid derivative are determined on a mole ratio basis. As mentioned above, the intermediate mixtures produced in the process of this invention can comprise other compounds in addition to the target intermediate species (e.g., imino or amide imidazoline intermediate species) specified for a particular process.
Thus, a composite molecular weight can be used to calculate the number of moles of a particular intermediate mixture. Theoretically, such a composite molecular weight determination could represent the molecular weights of all chemical species of the mixture and their respective mole percent contributions to the mixture composition. However, making such a determination requires time-consuming and tedious analysis of the mixture composition. Consequently, for convenience, the composite molecular weight for an intermediate mixture, produced by the processes of the present invention, was determined herein by presuming the mixture is primarily comprised of the target species. So, for example, the composite molecular weight assigned to the imino imidazoline mixture of Example 1 below is 389 grams/mole (i.e., the molecular weight of the target imidazoline), whereas the composite molecular weight assigned to the amide imidazoline mixture of Example 2 is 423 grams/mole (i.e., the molecular weight of the target imidazoline). Accordingly, such composite molecular weights can be used to calculate the number of moles of the mixture, and thereby determine the preferred amount of the third organic compound to be used in view of the mole ratio ranges specified below.
Preferably, the mole ratio of the target imino or amide intermediate mixture to the third organic acid or acid derivative is selected from the range of from about 1:1 to about 1:2.5. More preferably, the mole ratio of the target imino or amide intermediate mixture to the third organic acid or acid derivative is selected from the range of from about 1:1 to about 1:2. Most preferably, the mole ratio of the target imino or amide intermediate mixture to the third organic acid or acid derivative is selected from the range of from about 1:1 to about 1:1.5.
The corrosion inhibitors of the present invention can be used in any system exposed to fluids (i.e., liquid, gas, slurry or mixture thereof) containing a metal corrosion agent where improved corrosion inhibition is desired. However, the corrosion inhibitors of the present invention are particularly well-suited for use in oil and gas field applications and refinery operations.
With respect to such oil and gas field applications, the corrosion inhibitors of the present invention may be added to oil and/or gas fluids in the form of a solution or dispersion in water or an organic solvent. Examples of suitable solvents are alcohols such as methanol, ethanol, isopropanol, isobutanol, secondary butanol, glycols, and aliphatic and aromatic hydrocarbons.
The amount of active ingredient in a corrosion inhibitor formulation required to sufficiently reduce the rate of corrosion varies with the system in which it is used. Methods for monitoring the severity of corrosion in different systems are well-known to those skilled in the art, and may be used to decide the effective amount of active ingredient required in a particular situation. The compounds may be used to impart the property of corrosion inhibition to a composition for use in an oil or gas field application and may have one or more functions other than corrosion inhibition, e.g. scale inhibition.
The inhibitors of the type described herein have proven to be particularly effective for inhibiting corrosion of mild steel in hydrocarbon, oil/brine mixtures and aqueous systems under a variety of conditions. The inhibitor compositions claimed herein are preferably used in sweet systems, i.e., systems having a relatively high CO2 concentration. However, use of such compositions in systems having sour conditions (i.e., systems having a relatively high H2S concentration) is also acceptable. Although fluid content of flow lines may vary, the inhibitor may be used in a variety of environments. Oil cuts in the field can range from less than 1% (oil field) to 100% (refinery) oil, while the nature of the water can range from 0 to 300,000 ppm TDS (total dissolved solids). In addition, the inhibitor compositions of the present invention would also be useful in large diameter flow lines of from about 1 inch to about 4 feet in diameter, small gathering lines, small flow lines and headers. In a preferred method, the inhibitor composition is added at a point in the flow line upstream from the point at which corrosion prevention is desired.
In practice, the inhibitor compositions of the present invention are preferably added to the flow line continuously to maintain a corrosion inhibiting dose of from about 0.01 to about 5000 ppm. More preferably, the corrosion inhibiting dose is from about 0.1 to about 500 ppm. In a most preferred embodiment of the present invention, the corrosion inhibiting dose is from about 1 to about 250 ppm. Although a most preferred use of the corrosion inhibitor compositions of the present invention is for mild steel flow lines, it is believed that the inhibitor compositions are also effective in inhibiting corrosion in other types of metallurgy. In certain cases, batch treatments are the method of choice for application of the inhibitor compositions of the present invention. However, the invention can also be practiced using a continuous process. Dosage rates for batch treatments range from about 0.1 to about 50,000 ppm. In a preferred embodiment of the present invention, the flow rate of the flow line in which the inhibitor composition is used is between 0 and 100 feet per second. A more preferred flow rate is between 0.1 and 50 feet per second. In some cases, the inhibitors of the present invention may be formulated with water in order to facilitate addition to the flow line.
The inhibitors of the present invention may be used alone or in combination with other compounds. Typical formulations include pour point depressants and/or surfactants. Examples of suitable pour point depressants are C1 to C3 linear or branched alcohols, ethylene and propylene glycol. Examples of suitable surfactants are ethoxylated nonylphenols and/or ethoxylated amines as wetting agents or additives for dispersing the inhibitor into the fluid stream to which they are added. The surfactant is advantageously water soluble to allow the product to better wet the surface of the flow line where corrosion may take place. Water soluble surfactants utilized may be non-ionic, cationic or anionic and will generally have a hydrophilic-lipophilic (HLB) value of about 1. Oil soluble surfactants may be utilized if it is desired to disperse the inhibitor composition into a hydrocarbon fluid. Oil soluble surfactants may be non-ionic, cationic or anionic. These surfactants typically have an HLB value less than 7.
Other compounds which may also be blended with the inhibitor compositions claimed herein are quaternary amines, such as fatty, cyclic or aromatic amines quaternized with lower alkyl halides or benzyl chloride and certain amides. In addition, formulations including the inhibitors of the present invention may include filming agents such as p-toluenesulfonic acid and dodecylbenzenesulfonic acid. The corrosion inhibitor may also contain components which are typically included in corrosion inhibiting compositions, such as scale inhibitors and/or surfactants. In some instances, it may be desirable to include a biocide in the composition.
An example of a formulation which has been generally found to give superior performance is presented in Table I.
An example of a quaternary salt is an alkyl pyridine benzyl chloride quaternary salt. In the alkyl pyridine benzyl chloride quaternary salt, the alkyl group is preferably a methyl, ethyl or disubstituted alkyl group. The ethoxylated alkyl amine surfactant preferably has a carbon chain length of from about C10 to about C30 and preferably has about 20 moles of ethylene oxide per mole of amine.
The formulation is preferably produced by blending several ingredients into a homogeneous mixture. Though not critical to practicing the invention, the preferred order of addition is as follows: i) quaternized compound, ii) methanol and/or isopropanol, iii) quaternary salt, iv) ethoxylated alkyl amine surfactant, v) water and vi) p-toluenesulfonic acid.
The resultant inhibitor formulation may be used in a variety of petroleum operations in the oil and gas industry. It can be used to treat systems used in primary, secondary and tertiary oil and gas recovery. The inhibitor formulation may be introduced to such systems in accordance with techniques well-known to those skilled in the art. For example, one technique in which the inhibitor formulation can be used is the squeeze treating technique, whereby the inhibitor formulation is injected under pressure into a producing formation, adsorbed onto the strata and absorbed as the fluids are produced. The inhibitor formulation can further be added in water flooding operations of secondary oil recovery, as well as be added to pipelines, transmission lines and refinery units. The inhibitor formulation may also be used to inhibit acid solution in well-acidizing operations.
The following non-limiting examples of preferred compounds that may be made and used as claimed herein are provided for illustrative purposes only.
Also, it will be apparent to those skilled in the art, that the reaction schematics specifying particular intermediates and final products illustrate only those compounds which the Applicant presumes are significant compounds formed based on current principles of organic reaction chemistry and qualitative infrared analysis of the final reaction product. Illustration of a specified intermediate does not exclude the presence of other significant intermediate(s) important to the formation of the final product. Also, illustration of a final compound does not exclude the presence of other compounds in the final composition, including, without limitation, the unreacted starting reactants, intermediates and other final compound(s), if any, produced by competing reaction pathways.